Sadie, if you are a minor traveling without an adult you do not need identification if you are flying domestically. We do recommend that you bring something with your name and photo on it. We also recommend checking with the airline that you booked your flight on as they can provide assistance as well.
I'm not exactly sure on the details. Best way to find out is to go into the airport and ask them directly. I do know that when I flew as a minor years ago they made me wear this tag around my neck that stated I was a minor and an airport employee had to be with me at all times in the airport.
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